A Fresh Look At Weight-Estimation Models For Soil Mites (Acari)

Biomass data can be challenging to obtain for studies involving soil microarthropods, whose small body sizes make them difficult to weigh using anything but the most sensitive balances. Researchers can circumvent weighing by using aspects of body size (length, width and volume) to estimate biomass. However, size-based estimates are trustworthy only if they can be shown to correctly predict actual weights. Here, we provide a review of published weight-estimation models for soil mites (Arachnida: Acari) and test them using mites collected from grassland and woodland habitats in Alberta, Canada. Our analyses show that the models we tested mostly result in an underestimation of actual weight, although some show this bias more than others. Oribatida in particular suffer from this underestimation, while Prostigmata show some strong overestimations. However, some Oribatida weight prediction models work surprisingly well on other taxa. Based on these results, we provide suggestions of what models might be best used for different mite taxa.